1. Field of the Invention
The invention relates to a method of operating a gas turbine installation in which the air prepared in a compressor is mixed with a fuel downstream of the compression and is supplied to and burnt in a pressure-wave machine operating with constant-volume or constant-pressure combustion and the working gas obtained in this manner is subsequently admitted to a high-pressure gas turbine and a low-pressure gas turbine.
2. Discussion of Background
Such methods for preparing the working gas in gas turbine installations are known.
As an example, a method is described in U.S. Pat. No. 5,197,276 to Keller in which the combustion of the fuel/air mixture takes place in the rotor cells of a pressure-wave machine at constant volume and a part of the working gas forming due to the combustion in the rotor cells is admitted to a high-pressure gas turbine and the remaining part from the rotor cells is admitted to a low-pressure gas turbine. In operation, a homogeneous distribution of fuel is generated in the longitudinal direction of the cells in the pressure-wave machine. This produces problems where both a low-pressure turbine and a high-pressure turbine are connected to this pressure-wave machine because an attempt is made to operate both turbines at the same optimum temperature in order to improve efficiency, even though the gases are supplied at different pressures to the high-pressure turbine and the low-pressure turbine.
A method of operating a gas turbine installation with a pressure-wave machine operating with constant-volume combustion is known to the applicant, and in this method the compressed air has different enrichment with fuel from layer to layer so that, for example, one layer has a rich fuel/air mixture and one layer has a weak fuel/air mixture. After combustion, the layers are expanded to the same temperature and the partial quantity more strongly enriched with fuel is supplied to the high-pressure turbine and the partial quantity less strongly enriched with fuel is supplied to the low-pressure turbine. This increases the efficiency of the installation relative to the method published in U.S. Pat. No. 197,376 to Keller.
A gas turbine installation is also known in which the hot gas flow from the low-pressure driving-gas conduit connected to the pressure-wave machine is mixed with the hot gas flow which emerges from the high-pressure turbine, i.e. with partially expanded and cooled gas from the high-pressure turbine. This mixing takes place in the low-pressure turbine or, in part, before entry into the low-pressure turbine. The inlet temperature of the gas into the low-pressure turbine is reduced by the mixing of hot gas flows of different temperatures, and this has an unfavorable effect on the efficiency.